Manchester United used transfer deadline day to upgrade their attacking options after securing a deal to sign Radamel Falcao on loan having allowed Danny Welbeck to join Arsenal.

The Red Devils will pay Monaco between £5million and £6million for the Colombia striker and the club have confirmed they will cover the player's wages.

However, they insist reports they will pay the 28-year-old almost £350,000 a week are wide of the mark, although they left it late to complete the deal.

United had to gain an extension - allowed under Premier League rules on production of a declaration from all three parties of their intention to finalise the deal - in order to get the paperwork through but were still not in a position to announce the deal two and a half hours after the deadline had passed.

The delay on a move which had been in the pipeline all day sparked rumours Falcao, who recently recovered from a serious knee injury which kept him out of the World Cup, but United insisted throughout that was not true.

Arsenal confirmed the signing of Welbeck on a long-term contract, believed to be for £16million, at 1am leaving United officials waiting for confirmation from the Premier League all Falcao's paperwork was in order.

United also confirmed £14million Ajax defender Danny Blind had signed a four-year contract but it was the capture of Falcao - taking the club's spending past £150million this summer - which caught the imagination on a busy day for Premier League clubs.

The Colombian's arrival hastened the exit of Welbeck but manager Louis van Gaal will hope he can kick-start a stuttering start to the season which has seen them take just two points from three Premier League matches, scoring only two goals, without even taking into account their embarrassing Capital One Cup exit to League One MK Dons.

The day began with Falcao linked with last-minute moves to Manchester City and Arsenal, having previously been touted as a Real Madrid target.

As it turned out the latter two clubs benefited from Falcao choosing United as Welbeck went to the Emirates Stadium and Javier Hernandez headed to the Bernebeu on a season-long loan with an option to buy.

And United's near-neighbours City ended up a striker light after Alvaro Negredo signed for Valencia on loan, with a clause to make it permanent at the end of the season.

At Old Trafford Van Gaal also needed reinforcements in defence after the loss of key personnel over the summer and Blind will provide that.

"Louis van Gaal is a tremendously talented coach, I have worked with him at Ajax and also for the Netherlands national team and I cannot wait to work with him at the biggest club in the world," the Holland international told manutd.com.

Tom Cleverley looked to be moving to Aston Villa and then his preferred destination of Everton but the latter could not meet United's asking price.

However, United duo Nick Powell and Tom Lawrence both moved to Leicester on loan and permanent respectively.

Welbeck's need for more pitch time was no great secret but Arsenal's interest - and that of Tottenham - in the 23-year-old was not so well known.

But with Olivier Giroud out for four months with an ankle injury Gunners boss Arsene Wenger has bolstered his attacking ranks despite last week saying he would not sign anyone.

More than £826million was spent in total this summer with Hull making Uruguay striker Abel Hernandez their club record signing after bringing in the 24-year-old on a three-year deal from Palermo for a fee believes to be £9.5million, having earlier allowed winger George Boyd to join Burnley for a reported £3million.

Hernandez's compatriot Gaston Ramires joined him at the KC Stadium on loan from Southampton while midfielder Mohamed Diame moved from West Ham with Newcastle's Hatem Ben Arfa set to complete the Tigers' business once his paperwork was finalised.

Burnley also signed Chelsea's England Under-21 midfielder Nathaniel Chalobah on loan until January while another Chelsea player Marco van Ginkel temporarily moved to AC Milan.

QPR's bid to sign Fabio Borini collapsed, despite agreeing an initial £10million fee with Liverpool, as they could not agree personal terms but manager Harry Redknapp was reunited with midfielders Sandro, from Tottenham, on a three-year deal and Niko Kranjcar joining from Dynamo Kiev on loan.

Liverpool's Uruguay centre-back Sebastian Coates moved to Sunderland on loan while Reds winger Oussama Assaidi rejoined Stoke for a second season-long loan.

Crystal Palace signed Tottenham 21-year-old defender Zeki Fryers and Wigan midfielder James McArthur on three-year deals and also brought in Wolves striker Kevin Doyle on loan.

Marseille winger Morgan Amalfitano, who spent last season on loan at West Brom, joined West Ham permanently.

The signing of Falcao was the final chapter in a busy day for United with strikers Javier Hernandez and Danny Welbeck both leaving the club for Real Madrid and Arsenal respectively.

The loan fee for Falcao was thought to be between between £5million and £6million and the 28-year-old joined Daley Blind in moving to Manchester on Monday.

"I am delighted Radamel has joined us on loan this season," said United boss Louis van Gaal.

"He is one of the most prolific goalscorers in the game.

"His appearance-to-goal ratio speaks for itself and, when a player of this calibre becomes available, it is an opportunity not to be missed."

Falcao first came to prominence at Argentinian outfit River Plate and earned himself a move to Europe with Porto where he scored 72 goals in 87 appearances.

He continued that prolific form at Atletico Madrid, netting 70 goals in 91 appearances and earning a big-money move to Monaco last summer.

Falcao suffered a serious knee injury in January 2014 which forced him to miss the World Cup but he is now looking to play a big part in the new Van Gaal era at Old Trafford,

"I am delighted to be joining Manchester United on loan this season," he said.

"Manchester United is the biggest club in the world and is clearly determined to get back to the top.

"I am looking forward to working with Louis van Gaal and contributing to the team's success at this very exciting period in the club's history."

Welbeck's move to the capital had also gone to the wire, with the 23-year-old not being confirmed as a Gunner until the early hours after signing a long-term deal.

Hernandez's move to Spain is initially on loan with the European champions having an option to buy at the end of the spell.

Van Gaal will hope the changes can kick-start a stuttering start to the season which has seen United take just two points from three Premier League matches, scoring only two goals, without even taking into account their embarrassing Capital One Cup exit to League One MK Dons.

Van Gaal also needed reinforcements in defence after the loss of key personnel over the summer and the £14million capture of Blind on a four-year contract will boost a much-maligned backline.

"Louis van Gaal is a tremendously talented coach, I have worked with him at Ajax and also for the Netherlands national team and I cannot wait to work with him at the biggest club in the world," the Holland international told manutd.com.